162 research outputs found
A Higgs Mass Shift to 125 GeV and A Multi-Jet Supersymmetry Signal: Miracle of the Flippons at the \sqrt{s} = 7 TeV LHC
We describe a model named No-Scale F-SU(5) which is simultaneously capable of
explaining the dual signals emerging at the LHC of i) a 124-126 GeV Higgs boson
mass m_h, and ii) tantalizing low-statistics excesses in the multi-jet data
which may attributable to supersymmetry. These targets tend to be mutually
exclusive in more conventional approaches. The unified mechanism responsible
for both effects is the introduction of a rather unique set of vector-like
multiplets at the TeV scale, dubbed flippons, which i) can elevate m_h by
around 3-4 GeV via radiative loop corrections, and ii) flatten the running of
the strong coupling and color-charged gaugino, resulting in a prominent
collider signal from production of light gluino pairs. This well motivated
theoretical framework maintains consistency with all key phenomenological
constraints, and all residual parameterization freedom may in principle be
fixed by a combination of the two experiments described. We project that the
already collected luminosity of 5 fb^-1 may be sufficient to definitively
establish the status of this model, given appropriate data selection cuts.Comment: Physics Letters B version, 10 pages, 3 figures, 2 tables. arXiv admin
note: text overlap with arXiv:1105.398
The Tevatron at the Frontier of Dark Matter Direct Detection
Direct detection of dark matter (DM) requires an interaction of dark matter
particles with nucleons. The same interaction can lead to dark matter pair
production at a hadron collider, and with the addition of initial state
radiation this may lead to mono-jet signals. Mono-jet searches at the Tevatron
can thus place limits on DM direct detection rates. We study these bounds both
in the case where there is a contact interaction between DM and the standard
model and where there is a mediator kinematically accessible at the Tevatron.
We find that in many cases the Tevatron provides the current best limit,
particularly for light dark matter, below 5 GeV, and for spin dependent
interactions. Non-standard dark matter candidates are also constrained. The
introduction of a light mediator significantly weakens the collider bound. A
direct detection discovery that is in apparent conflict with mono-jet limits
will thus point to a new light state coupling the standard model to the dark
sector. Mono-jet searches with more luminosity and including the spectrum shape
in the analysis can improve the constraints on DM-nucleon scattering cross
section.Comment: 20 pages, 8 figures, final version in JHE
The Higgs as a Probe of Supersymmetric Extra Sectors
We present a general method for calculating the leading contributions to h ->
gg and h -> gamma gamma in models where the Higgs weakly mixes with a nearly
supersymmetric extra sector. Such mixing terms can play an important role in
raising the Higgs mass relative to the value expected in the MSSM. Our method
applies even when the extra sector is strongly coupled, and moreover does not
require a microscopic Lagrangian description. Using constraints from holomorphy
we fix the leading parametric form of the contributions to these Higgs
processes, including the Higgs mixing angle dependence, up to an overall
coefficient. Moreover, when the Higgs is the sole source of mass for a
superconformal sector, we show that even this coefficient is often calculable.
For appropriate mixing angles, the contribution of the extra states to h -> gg
and h -> gamma gamma can vanish. We also discuss how current experimental
limits already lead to non-trivial constraints on such models. Finally, we
provide examples of extra sectors which satisfy the requirements necessary to
use the holomorphic approximation.Comment: v4: 34 pages, 2 figures, typo corrected and clarification adde
Astrophysical Uncertainties in the Cosmic Ray Electron and Positron Spectrum From Annihilating Dark Matter
In recent years, a number of experiments have been conducted with the goal of
studying cosmic rays at GeV to TeV energies. This is a particularly interesting
regime from the perspective of indirect dark matter detection. To draw reliable
conclusions regarding dark matter from cosmic ray measurements, however, it is
important to first understand the propagation of cosmic rays through the
magnetic and radiation fields of the Milky Way. In this paper, we constrain the
characteristics of the cosmic ray propagation model through comparison with
observational inputs, including recent data from the CREAM experiment, and use
these constraints to estimate the corresponding uncertainties in the spectrum
of cosmic ray electrons and positrons from dark matter particles annihilating
in the halo of the Milky Way.Comment: 21 pages, 9 figure
Decaying Dark Matter in Supersymmetric Model and Cosmic-Ray Observations
We study cosmic-rays in decaying dark matter scenario, assuming that the dark
matter is the lightest superparticle and it decays through a R-parity violating
operator. We calculate the fluxes of cosmic-rays from the decay of the dark
matter and those from the standard astrophysical phenomena in the same
propagation model using the GALPROP package. We reevaluate the preferred
parameters characterizing standard astrophysical cosmic-ray sources with taking
account of the effects of dark matter decay. We show that, if energetic leptons
are produced by the decay of the dark matter, the fluxes of cosmic-ray positron
and electron can be in good agreements with both PAMELA and Fermi-LAT data in
wide parameter region. It is also discussed that, in the case where sizable
number of hadrons are also produced by the decay of the dark matter, the mass
of the dark matter is constrained to be less than 200-300 GeV in order to avoid
the overproduction of anti-proton. We also show that the cosmic gamma-ray flux
can be consistent with the results of Fermi-LAT observation if the mass of the
dark matter is smaller than nearly 4 TeV.Comment: 24 pages, 5 figure
The Supersymmetric Standard Models with Decay and Stable Dark Matters
We propose two supersymmetric Standard Models (SMs) with decaying and stable
dark matter (DM) particles. To explain the SM fermion masses and mixings and
have a heavy decay DM particle S, we consider the Froggatt-Nielsen mechanism by
introducing an anomalous U(1)_X gauge symmetry. Around the string scale, the
U(1)_X gauge symmetry is broken down to a Z_2 symmetry under which S is odd
while all the SM particles are even. S obtains a vacuum expectation value
around the TeV scale, and then it can three-body decay dominantly to the
second/third family of the SM leptons in Model I and to the first family of the
SM leptons in Model II. Choosing a benchmark point in the constrained minimal
supersymmetric SM with exact R parity, we show that the lightest neutralino DM
is consistent with the CDMS II experiment. Considering S three-body decay and
choosing suitable parameters, we show that the PAMELA and Fermi-LAT experiments
and the PAMELA and ATIC experiments can be explained in Model I and Model II,
respectively.Comment: RevTex4, 26 pages, 6 figures, references added, version to appear in
EPJ
Solving the mu problem with a heavy Higgs boson
We discuss the generation of the mu-term in a class of supersymmetric models
characterized by a low energy effective superpotential containing a term lambda
S H_1 H_2 with a large coupling lambda~2. These models generically predict a
lightest Higgs boson well above the LEP limit of 114 GeV and have been shown to
be compatible with the unification of gauge couplings. Here we discuss a
specific example where the superpotential has no dimensionful parameters and we
point out the relation between the generated mu-term and the mass of the
lightest Higgs boson. We discuss the fine-tuning of the model and we find that
the generation of a phenomenologically viable mu-term fits very well with a
heavy lightest Higgs boson and a low degree of fine-tuning. We discuss
experimental constraints from collider direct searches, precision data, thermal
relic dark matter abundance, and WIMP searches finding that the most natural
region of the parameter space is still allowed by current experiments. We
analyse bounds on the masses of the superpartners coming from Naturalness
arguments and discuss the main signatures of the model for the LHC and future
WIMP searches.Comment: Extended discussion of the LHC phenomenology, as published on JHEP
plus an addendum on the existence of further extremal points of the
potential. 47 pages, 16 figure
Semi-homomorphic Encryption and Multiparty Computation
An additively-homomorphic encryption scheme enables us to compute
linear functions of an encrypted input by manipulating only the ciphertexts. We define the relaxed notion of a semi-homomorphic
encryption scheme, where the plaintext can be recovered as long as the
computed function does not increase the size of the input too
much . We show that a number of existing cryptosystems are
captured by our relaxed notion. In particular, we give examples of semi-homomorphic encryption schemes based on lattices, subset sum and factoring.
We then demonstrate how semi-homomorphic encryption schemes allow us
to construct an efficient multiparty computation protocol for arithmetic circuits, UC-secure against a dishonest majority. The protocol consists of a preprocessing phase and an online phase. Neither the inputs nor the function to be computed have to be known during preprocessing.
Moreover, the online phase is extremely efficient as it requires
no cryptographic operations: the parties only need to exchange additive shares and verify information theoretic MACs.
Our contribution is therefore twofold: from a theoretical point of view, we can base multiparty computation on a variety of different assumptions, while on the practical side we offer a protocol with better efficiency than any previous solution
Precision Unification in \lambda SUSY with a 125 GeV Higgs
It is challenging to explain the tentative 125 GeV Higgs signal in the
Minimal Supersymmetric Standard Model (MSSM) without introducing excessive
fine-tuning, and this motivates the study of non-minimal implementations of low
energy supersymmetry (SUSY). A term \lambda SH_uH_d involving a Standard Model
(SM) singlet state S leads to an additional source for the quartic interaction
raising the mass of the lightest SM-like Higgs. However, in order to achieve
m_h \approx 125 GeV with light stops and small stop mixing, it is necessary for
\lambda \gtrsim 0.7 and consequently \lambda may become non-perturbative before
the unification scale. Moreover, as argued by Barbieri, Hall, et al. low
fine-tuning prefers the region \lambda~1-2, leading to new or non-perturbative
physics involving S below the GUT scale (`\lambda SUSY' models). This raises
the concern that precision gauge coupling unification, the prime piece of
indirect experimental evidence for low energy SUSY, may be upset. Using the
NSVZ exact \beta-function along with well motivated assumptions on the strong
coupling dynamics we show that this is not necessarily the case, but rather
there exist classes of UV completions where the strong-coupling effects can
naturally correct for the present ~3% discrepancy in the two-loop MSSM
unification prediction for \alpha_s. Moreover, we argue that in certain
scenarios a period of strong coupling can also be beneficial for t-b
unification, while maintaining the small to moderate values of tan\beta
preferred by the Higgs mass.Comment: 16 pages, 5 figures, v2. Discussion regarding evolution of Yukawa
couplings and t-b unification added, accepted for publication in JHE
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